JP3839989B2 - Image processing method and apparatus, recording method and apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an image processing method and apparatus for creating image data for recording an image using recording agents having different concentrations, and a recording method and device for recording images using recording agents having different concentrations. .
[0002]
[Prior art]
Recording apparatuses such as printers, copiers, and facsimiles are configured to record an image composed of a dot pattern on a recording medium such as paper or a plastic thin plate based on image information. Such recording apparatuses are classified into, for example, an ink jet type, a wire dot type, a thermal type, a laser beam type, and the like according to the recording method. Among these, the ink jet type (ink jet recording apparatus) is configured to discharge and eject ink (recording liquid) droplets from the discharge port of the recording head and attach them to a recording medium for recording.
[0003]
In recent years, with the widespread use of computers, a large number of recording devices have been used, and demands for high-speed recording, high resolution, high image quality, low noise, and the like are increasing. As a recording apparatus that meets such a demand, the above-described ink jet recording apparatus is relatively popular, and is rapidly spreading because it can easily cope with colorization.
[0004]
In order to improve the recording speed, an ink jet recording apparatus often uses a recording head in which a plurality of ink discharge ports (nozzles) are integrated and a plurality of recording heads corresponding to colors. . Moreover, halftone processing methods such as a dither method and an error diffusion method are used as methods for faithfully reproducing the gradation of image information in these ink jet recording apparatuses because of demands for high resolution and high image quality.
[0005]
In these gradation reproduction methods, excellent gradation recording is possible when the resolution of the recording apparatus is sufficiently high (about 1000 dots / inch or more). However, when the resolution of the recording apparatus is low (about 360 to 720 dots / inch), the recording dots in the highlight portion are conspicuous, and a rough feeling of the image tends to occur due to discontinuity of pixels. Therefore, in order to further increase the number of gradations, a method of multi-leveling the recording dots themselves has been performed. For example, a method is known in which gradation is reproduced by modulating the diameter of a recording dot attached to a recording medium by controlling the voltage or pulse width applied to the recording head. However, such a method is highly environment-dependent, and the recording dot diameter is not stable, and there is a limit to the size of the minimum recording dot that can be recorded, so that it is difficult to reproduce the gradation stably.
[0006]
In addition, there is a density modulation method that changes the density of dots in the dot matrix (predetermined area) while keeping the dot size constant. However, in order to increase the number of gradations, a considerable area is required for one pixel. Therefore, the resolution becomes worse.
[0007]
Therefore, as a method for improving gradation characteristics and obtaining a high-density and high-gradation image using such an ink jet recording apparatus, a plurality of liquid droplets are landed on substantially the same location on a recording medium. At least two types of similar colors using a so-called multi-droplet method, in which gradation is expressed by changing the number of droplets landed there, and a plurality of inks having different densities A recording system that reproduces gradation using recording dots having different densities or a system that combines these two systems has been proposed and put to practical use.
[0008]
[Problems to be solved by the invention]
In general, it is known that the concentration of ink in the head increases with time because the solvent of the ink contained in the ink jet head gradually evaporates. As a result, especially in the multi-droplet method and the inkjet method in which an image representing gradation is recorded using inks of similar colors and different densities, the balance of the gradation to be reproduced is lost due to fluctuations in the density of the ink, and the reproduction is performed. In some cases, the smoothness of gradation in the image is lost, and a pseudo contour is generated, so that the quality of the reproduced image is impaired.
[0009]
Further, as a recording medium (recording sheet) on which recording is performed, it is conceivable that ten or more kinds of recording media having different image quality, durability, price, and the like are used according to the purpose. In this case, depending on the combination of the recording sheet and ink, or the combination of the types of ink to be overprinted, etc., the ink absorption amount, the ink absorption speed, the size of the generated dot diameter, and the like differ in the recorded image. Concentration jumps may occur depending on the density, or the density may be reversed. It is also conceivable that density jumps occur between inks having different densities because the rate of density change due to evaporation of the ink solvent described above is not constant. For these reasons, the gradation of the reproduced image density may deteriorate to a degree that cannot be corrected by normal calibration.
[0011]
The present invention has been made in view of the above conventional example, and is used for recording corresponding to the image density. Combination of multiple types of ink A plurality of tables for determining the image, an image processing method and apparatus for selecting an optimum table based on the recording density of the actually recorded test pattern, and recording the image, and the image It is an object of the present invention to provide a recording method and apparatus for recording an image.
[0012]
Another object of the present invention is to use for recording corresponding to image density. Combination of multiple types of ink A plurality of tables storing information for determining the recording density were prepared, and the recording density of the test pattern recorded using each table and the recording density were realized. Multiple types of ink It is an object to provide an image processing method and apparatus for processing so as to record an image using a table having the largest correlation with the density signal level corresponding to the combination, and a recording method and apparatus for recording the image.
[0013]
[Means for Solving the Problems]
In order to achieve the above object, the image processing apparatus of the present invention comprises the following arrangement. That is,
Different concentrations Similar color ink Multiple For seeds And an image processing device for recording pixels,
Used to record pixels with multiple levels of density signal level Multiple types of ink Storage means for storing a plurality of types of tables defining combinations of
Recording means for recording a plurality of types of test patterns on the recording medium, each of the plurality of types of density signal levels using each of the plurality of types of tables;
Measuring means for measuring the recording density of each of the test patterns recorded on the recording medium by the recording means;
Realized the recording density measured by the measuring means and the recording density Multiple types of ink Selection means for selecting a table with the highest density gradation reproducibility from the plurality of types of tables based on the density signal level corresponding to the combination of
The table corresponding to the density signal level of each pixel constituting the image data using the table selected by the selection means. Multiple types of ink Generating means for generating recording data for recording using a combination of
The plurality of types of tables have the same density signal level on the low density side of the plurality of density signal levels. all the same Said Define the combination And , Excluding maximum concentration On the high concentration side, the same concentration signal level Multiple types of said A combination is defined.
[0014]
In order to achieve the above object, the image processing method of the present invention comprises the following steps. That is,
Different concentrations at different concentrations Similar color ink Multiple For seeds An image processing method for recording pixels,
Used to record pixels of multiple levels of density signal levels Multiple types of ink A step of reading out the plurality of types of tables from the storage means storing a plurality of types of tables defining the combination of:
A recording step of recording a test pattern including pixels of the plurality of levels of density signal levels on the plurality of types of recording media using each of the plurality of types of read tables;
A measuring step of measuring a recording density of each of the test patterns recorded on the recording medium in the recording step;
Realized the recording density measured in the measuring step and the recording density Multiple types of ink A selection step of selecting a table having the best reproducibility of the density gradation from the plurality of types of tables based on the density signal level corresponding to the combination of:
Using the table selected in the selection step, the density signal level corresponding to the density signal level of each pixel constituting the image data Multiple types of ink Generating recording data for recording using a combination of
The plurality of types of tables have the same density signal level on the low density side of the plurality of density signal levels. all the same Said Define the combination And , Excluding maximum concentration On the high concentration side, the same concentration signal level Multiple types of said A combination is defined.
[0015]
In order to achieve the above object, the recording apparatus of the present invention has the following configuration. That is,
Different concentrations Similar color ink Multiple For seeds A recording device for recording an image on a recording medium,
Claim 1 Or 2 An image processing apparatus according to claim 1,
Control means for driving the recording means based on the recording data generated by the generating means of the image processing apparatus and controlling to record an image based on the input image data. To do.
[0016]
In order to achieve the above object, the recording method of the present invention comprises the following steps. That is,
Different concentrations Similar color ink Multiple For seeds And a recording method for recording an image on a recording medium,
Claim 3 or 4 An image processing method described in
A control step for controlling to record an image based on the input image data based on the recording data generated in the generation step in the image processing method;
It is characterized by having.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
DESCRIPTION OF EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the present embodiment, in order to simplify the description, an example in which a monochrome image is recorded using an additive ink / film system will be described.
[0018]
[Additivity]
First, an additive ink / film system means that when an image is recorded on a transmission film used for recording a transmission image by an ink jet method, the ink is overprinted multiple times at the same pixel position. This means that the density of the pixel is the sum of the densities when the inks are individually recorded.
[0019]
An example where this additivity holds is given.
[0020]
As a recording medium (recording sheet), on a transparency film (CF-301), a dye-based C.I. I. When a 2% solution of Direct Black 19 is uniformly recorded using an ink jet printer, an image having a transmission density of “0.8D” is obtained. I. When uniformly recorded using a 1% solution of Direct Black 19, an image having a transmission density of “1.2D” is obtained. In this ink / film system, it has been confirmed by experiments that the additivity substantially holds in the range of “0” to “2.5D”.
[0021]
In such an ink / film system having an additive property, the number of gradations that can be expressed can be greatly increased by overprinting a plurality of types of inks having different densities at the same pixel position.
[0022]
[Ink density]
Next, the ink density of the inkjet head unit will be described.
[0023]
First, consider a case where an image is recorded using four types of ink. Here, when the ink can be overprinted four times without overflowing on the recording medium and the additivity is satisfied, the density ratio of the inks D1, D2, D3, and D4 is set to “1: 2. : 4: 6 ", the number of gradations can be maximized by changing the combination of ejected inks.
[0024]
FIG. 3 shows an ink type distribution table that stores information indicating the presence or absence of ink ejection for image data. In the figure, d1 to d4 are data representing the presence or absence of ejection for the inks D1 to D4. If the value is “1”, the ink is ejected, and if it is “0”, it is binary data meaning no ejection. . As an example, when the pixel value (density value) of the image data is “10”, the inks of D3 and D4 are ejected in an overlapping manner on the pixel.
[0025]
When the density ratio of these four types of ink is “1: 2: 4: 6” as described above, the density value is “0” by the combination of the presence or absence of ejection of each ink based on the ink type distribution table 4b. "To" 13 "can be expressed without skipping density.
[0026]
Further, when the ink density fluctuates due to ink evaporation in the ink tank and nozzles, it can be changed to another ink type distribution table. In this way, by selecting an optimum one from a plurality of ink type distribution tables, it is possible to perform density gradation correction described in detail later.
[0027]
The present embodiment will be described below with reference to the drawings. In the present embodiment described below, the configuration of the ink jet recording apparatus will be described. However, the present invention is not limited to this. For example, the conversion processing from image data to recording data in the present embodiment is a host. It may be performed by a computer device such as a computer, or may be executed by a printer driver or the like.
[0028]
In this embodiment, an example of an ink jet recording apparatus will be described. However, the present invention is not limited to this, and may be, for example, a color thermal transfer recording apparatus.
[0029]
[Embodiment 1]
FIG. 1 is a block diagram showing the configuration of the ink jet recording apparatus according to the first embodiment.
[0030]
In FIG. 1, 1 is an image input unit such as a scanner, 2 is an operation unit having various keys for setting various parameters and instructing printing start, and 3 is an entire recording apparatus according to various programs stored in a storage medium 4. It is CPU which controls. The storage medium 4 stores a program for operating the recording apparatus in accordance with a control program and an error processing program. All operations in the present embodiment are executed based on this program. As the storage medium 4 for storing such a program, ROM, FD, CD-ROM, HD, memory card, magneto-optical disk, or the like can be used.
[0031]
In the storage medium 4, 4a is a gamma correction conversion table for reference in gamma conversion processing, 4b is an ink type distribution table for reference in ink type distribution processing described later, 4c is test pattern information, 4d is for storing various programs. Each program group is shown.
[0032]
Reference numeral 5 denotes a RAM which is used as a work area for various programs in the storage medium 4, a temporary save area for error processing, and a work area for image processing. It is also possible to copy the various tables and data 4a to 4c of the recording medium 4 to the RAM 5, change the contents of the tables and data, and perform image processing to be described later with reference to the changed table. . Reference numeral 6 denotes an image processing unit which creates recording data for realizing multi-gradation by an ink jet method based on input image data. A printer unit (printer engine) 7 forms a dot image on a recording medium such as a recording sheet based on recording data created by the image processing unit 6 at the time of image recording. A test pattern density measuring unit 8 measures the density of the test pattern recorded on the recording medium and updates and changes the ink type distribution table 4b based on the measurement result, as will be described later. Reference numeral 9 denotes a bus line that connects the above-described units and transmits address signals, data, control signals, and the like.
[0033]
Next, a rough process of the image processing unit 6 according to the present embodiment will be described with reference to FIG.
[0034]
FIG. 2 is a diagram showing a flow of processing in the image processing unit 6 of the present embodiment.
[0035]
The image signal CV input by the image input unit 1 is input to the gamma correction processing 11 and converted into a density signal CD representing the density with reference to the gamma correction conversion table 4a. The density signal CD of the image subjected to gamma correction in this way is stored in the page memory area of the image processing work area of the RAM 5.
[0036]
The target pixel selection process 12 selects one pixel (target pixel) to be processed in the page memory area of the RAM 5 and obtains density data CD of the selected pixel. In the ink type distribution process 13, ink for expressing the density CD of the target pixel by referring to the ink type distribution table 4 b based on the density value (CD value) of the target pixel selected in the target pixel selection process 12. Select a combination candidate.
[0037]
By performing the above processing, the binary data determination processing for recording the target pixel is completed.
[0038]
In the printer unit 7, ink is ejected from the corresponding ink ejection port array in accordance with binary data d1, d2, d3,... From an inkjet head unit having different densities, thereby forming a multi-tone image. In FIG. 2, reference numerals 17-1, 17-2,... Denote delay circuits, which act to take the timing for overprinting ink at the same pixel position from each ink ejection row.
[0039]
Next, the printer unit 7 of the present embodiment will be described with reference to FIG.
[0040]
FIG. 4 is an overview diagram showing the configuration of the main part of the printer unit 7 of the present embodiment.
[0041]
On the carriage 20, a plurality of inkjet head units 21-1 to 21-4 are placed. Each inkjet head unit 21 is provided with an ejection port (nozzle) row for ejecting ink, and each inkjet head unit 21 is installed at a predetermined interval. As a result, the interval between the nozzle rows of each inkjet head unit 21 is also a predetermined interval. The ink supplied to each nozzle row of each inkjet head unit 21-1 to 21-4 is supplied from each of the ink cartridges 22-1 to 22-4, and each of the ink cartridges 22-1 to 22-4. Is an ink cartridge for supplying each ink D1, D2, D3, D4. The density of the ink stored in each cartridge will be described later. Control signals, recording signals, and the like to the inkjet head unit 21 are sent from the image processing unit 6 via the flexible cable 23.
[0042]
Reference numeral 24 denotes a recording medium, which is, for example, paper or a plastic thin plate, and is sandwiched between paper discharge rollers 25 via a conveyance roller (not shown), and is sent in the direction of the arrow as the conveyance motor 26 is driven to rotate. Reference numeral 27 is a guide shaft for guiding and supporting the traveling of the carriage 20, and 28 is a linear encoder, which detects the traveling position of the carriage 20. The carriage 20 is transported and driven via the drive belt 29 by the rotational drive of the carriage motor 30 and is reciprocated along the guide shaft 27.
[0043]
A heating element (electric / thermal energy converter) that generates thermal energy for ink ejection is provided in the ink ejection port (liquid path) of the inkjet head unit 21 described above. Along with the reading timing of the linear encoder 28, the heating element is driven based on the recording data, and ink droplets are ejected and adhered onto the recording medium 24 in the order of the inks D1, D2, D3, and D4. An image can be formed on the recording medium 24.
[0044]
At the home position of the carriage 20 set outside the recording area by the ink jet head unit 21, a recovery unit 32 including cap portions 31-1 to 31-4 is installed. Thus, when recording is not performed, the carriage 20 is moved to the home position, and the ink discharge port surfaces of the corresponding inkjet head units 21-1 to 21-4 are sealed by the caps 31-1 to 31-4 of the cap portion 31. In addition, clogging due to sticking of ink or adhesion of foreign matters such as dust due to evaporation of the ink solvent in the ejection port is prevented.
[0045]
Further, the cap unit 31 is used for idle ejection in which ink is ejected to the cap unit 31 in a state of being separated from the ink ejection port in order to eliminate ejection failure and clogging of the ink ejection port with low recording frequency. Further, a pump (not shown) is operated in a state where the ink discharge port is capped by the cap unit 31, and the ink is sucked from the ink discharge port, thereby being used for discharge recovery of the discharge port in which the discharge failure has occurred. An ink receiver 33 is used to perform preliminary ejection toward the ink receiver 33 when each of the inkjet head units 21-1 to 21-4 passes over the ink receiver 33 immediately before recording. In addition, by arranging a blade and a wiping member (not shown) adjacent to the cap portion 31, it is possible to clean the ink discharge port forming surfaces of the inkjet head units 21-1 to 21-4.
[0046]
In the vicinity of the outlet of the recording medium 24, a density measuring unit 8 for measuring the density of the recorded test pattern is supported by a support means (not shown). The concentration measuring unit 8 includes, for example, a light source such as an LED, a photodetector such as a phototransistor, and a measurement circuit that inputs an electrical signal output from the photodetector. That is, the intensity of transmitted light emitted from the light source and passed through the recording medium 24 is detected by a photodetector, and the density of the test pattern recorded on the recording medium 24 is measured. The density measuring unit 8 calculates the transmission density of each gradation pattern immediately after printing the gradation test patterns as indicated by reference numerals 601 to 603 in FIG. 6, and data for performing automatic calibration according to the measured density. Create It should be noted that the present invention is not limited to such a density measurement of a transmission image. For example, when the density is measured by irradiating the test pattern of the recording medium 24 from a light source and reading the reflected light. Needless to say, it can be applied.
[0047]
FIG. 5 is a view of the arrangement of the ink ejection port (nozzle) rows of the inkjet head units 21-1 to 21-4 as viewed from the recording medium 24 side. With reference to FIG. 5, the configuration of the ink discharge port array and the image configuration example in the printer unit 7 of the present embodiment will be described.
[0048]
In FIG. 5, each of 40-1 to 40-4 is an ejection port array that ejects each of the inks D1 to D4. The ejection port array of each unit has a pitch of 600 dots per inch (600 dpi) and is vertical ( There are 256 discharge ports in the (sub-scan) direction. In this way, an image having a 256-dot width in which four types of ink D1 to D4 are superimposed in the sub-scanning direction can be formed by one scan of the carriage 20 in the main scanning direction. As a result, it is possible to shorten the printing time and generate a high gradation image.
[0049]
[Auto density calibration]
Next, a description will be given of an automatic calibration method that is performed so that the density gradation of an image on a recording medium is always good when printing is performed using the ink jet recording apparatus of the present embodiment.
[0050]
FIG. 7 is a flowchart showing the procedure of automatic calibration in the present embodiment.
[0051]
First, as shown in FIG. 6, a density gradation test pattern is obtained using each of a plurality of (three types of tables # 1 to # 3) ink type distribution tables shown in FIGS. Recording is performed on one recording medium (step S1). In step S2, the density measurement unit 8 of the printer unit 7 measures the density of the test pattern recorded based on each ink type distribution table. Next, in step S3, for each ink type distribution table, the measured density is linearly approximated to the density level of the image signal using the least square method. In step S4, an ink type distribution table having the largest correlation coefficient of the least square method is obtained. Here, since the ink type distribution table having the largest correlation coefficient of the least squares method is considered to be the data table having the best gradation reproducibility, this table is set in the ink type distribution table 4b of the storage medium 4. Then, the print unit 7 is set in the ready state and is in a standby state. Thus, when performing subsequent printing, the ink type distribution table 4b is used to determine the ink jet head unit to be used according to the density value of the image, and printing is executed accordingly.
[0052]
Next, the calibration operation in step S4 will be described in more detail with reference to FIG.
[0053]
As described above, the storage medium 4 corresponds to a plurality of ink type distribution tables # 1, # 2, and # 3 (FIG. 8) and a gradation density pattern having an image density of about 16 gradations as test pattern information. Assume that image data to be stored is stored in advance.
[0054]
In the present embodiment, combinations of three ink types (three tables) are stored as a plurality of ink type distribution tables corresponding to the range of image density signal levels 8-14. The reason why a plurality of combinations are prepared in a region where the image density is high in this way is that the high density ink used for expressing a high image density has a greater influence on the density change.
[0055]
Also, since the effects of changes over time are likely to appear in the direction of increasing ink density, prepare a table with a lower transmission density than the predicted transmission density of the reference table, or predict the number of tables with a lower predicted transmission density. It is desirable to increase the number of tables having a high transmission density.
[0056]
When the apparatus is turned on, or before the operator uses the printer unit 7 or when the ink or recording medium is changed, or when the head is replaced, etc. The automatic calibration (calibration) operation of the present embodiment is started at an arbitrary timing or periodically by pressing an automatic calibration start button (not shown) in the operation unit 2 or by an instruction from the host side.
[0057]
First, the ink type distribution table # 1 is written in the ink type distribution table 4b of the storage medium 4. Next, the image data of the test pattern is input to the image processing unit 6 as the image signal CV. This image data is converted into a signal CD representing density using the gamma correction conversion table 4 a, and the density signal is stored in the page memory area of the image processing work area of the RAM 5.
[0058]
Next, one pixel (target pixel) of the test pattern converted to this density signal is selected, and density data CD of that pixel is obtained. Based on the obtained density data CD, the ink type distribution table # 1 is referred to determine an ink combination for recording the pixel, and the pixel is recorded corresponding to each inkjet head unit. .., Binary data d1, d2, d3,... Indicating ink ejection or non-ejection. In accordance with the generated binary data, ink is ejected from each corresponding inkjet head unit, and the pixel is recorded. By sequentially executing such processing on other pixels, the test pattern is recorded based on the binary data created using the ink type distribution table # 1.
[0059]
When the recording of the test pattern is thus completed, the ink type distribution table 4b is then rewritten to the ink type distribution table # 2. Again, based on the same test pattern data, this time, using the ink type distribution table # 2, the combination of inkjet head units used for recording is determined, and recording is performed on the recording medium in the same manner as described above.
[0060]
Similarly, recording is performed based on the binary data determined in the ink type distribution table # 3, and finally a test pattern recording result as shown in FIG. 6 is obtained. In FIG. 6, for example, 601 shows the result of recording using the ink type distribution table # 1, 602 shows the result of recording using the ink type distribution table # 2, and 603 shows the result of recording using the ink type distribution table # 3. Each result is shown.
[0061]
Here, as shown in FIG. 6, since the gradation patterns are recorded so as to be arranged in a line, only one optical sensor of the density measuring unit 8 is required, and there is an advantage that the density can be accurately measured with a simple configuration. is there. In addition, since recording is continuously performed on one recording medium, the number of recording media required for calibration can be minimized, and accurate density measurement and calibration can be performed without being affected by each variation of the recording medium. Will be done.
[0062]
Next, when the recording medium is discharged from the printing unit 7, each density is measured by the density measuring unit 8. That is, the recording medium on which the gradation pattern is recorded is conveyed by the paper discharge roller 25 in the arrangement direction of the gradation pattern, and the density pattern of each gradation passes one after another through the density measuring unit 8, and the density thereof is Measured automatically.
[0063]
Here, the density of each gradation pattern measured with respect to the image data of each gradation is plotted as shown in FIG. In this way, different density gradations can be obtained due to the difference in the characteristics of the ink type distribution table.
[0064]
FIG. 9 shows an example in which the actual measured densities are plotted when the densities of the inks D3 and D4 increase by 5% and 20%, respectively, to become “0.42D” and “0.72D”, respectively. Yes. This plot is for explanation of the present embodiment and does not need to be performed by actual automatic calibration.
[0065]
Here, in order to obtain an optimum table from among a plurality of ink type distribution tables (# 1 to # 3), in the automatic calibration processing of the present embodiment, the density is saturated after recording the test pattern and measuring the density. For the 14 gradations (image density levels “0” to “13”) excluding the portion, linear approximation is performed by the least square method based on the difference between the density data measured from the recording result and the original image data. Find the correlation coefficient between. Here, since the ink type distribution table having the largest correlation function is considered to have the best density gradation reproducibility, the ink type distribution table is written in the ink type distribution table 4b of the storage medium 4, and then calibration is performed. Up to now, the ink type distribution table used for actual recording is used. Based on the ink type distribution table 4b determined in this way, an inkjet head unit to be used for recording is determined corresponding to the image density, and recording is performed based on the determined data (binary data).
[0066]
In the example of FIG. 9, the correlation coefficient when the measured density of the gradation pattern recorded using each of the ink type distribution tables # 1, # 2, and # 3 is linearly approximated as described above is “0”. .997 ”,“ 0.999 ”, and“ 0.994 ”. As a result, the ink type distribution table # 2 having the largest correlation coefficient is determined as the ink type distribution table having the best gradation, and this ink type distribution table # 2 is written in the ink type distribution table 4b of the storage medium 4. In the subsequent recording process (shown in the flowchart of FIG. 2), this table 4b is used.
[0067]
In this embodiment, the ink type distribution table is evaluated using the correlation coefficient of the least square method. However, the present invention is not limited to this method, and other evaluation methods are used to optimize the ink type distribution table. Ink type distribution table may be selected.
[0068]
In this embodiment, the case where four types of ink are used has been described. However, the present invention is not limited to this. In addition, the number of ink type distribution tables prepared in advance is not limited to three, and by preparing more ink type distribution tables, ink types having optimum tone reproduction characteristics even when ink density changes are large. A distribution table can be selected.
[0069]
Further, the test pattern is not limited to the pattern shown in FIG. 6, and optimal calibration can be performed by using a test pattern having an optimum shape and an optimum gradation pattern according to the measurement form.
[0070]
In this embodiment, test printing is performed using an ink type distribution table prepared in advance. However, a new ink type distribution table can be created based on the result of density measurement of a test pattern. It is also possible to prepare an ink type distribution table corresponding to the degree of density change by modifying the ink type distribution table, and to perform test printing using a plurality of ink type distribution tables including these ink type distribution tables.
[0071]
In this embodiment, the density measurement of the test pattern is automatically performed, but only the density measurement is performed by another system, and the measured density data is transferred or input by the operator from the control panel or the like. Similarly, the optimum ink type distribution table can be selected and recorded.
[0072]
In the present embodiment described above, means (for example, an electrothermal converter or a laser beam) that generates thermal energy as energy used to perform ink ejection is provided, and the thermal energy causes a change in the state of the ink. However, the present invention is not limited to this, and the present invention can also be applied to a method using a piezoelectric element as means for ejecting ink. According to such a system, it is possible to achieve higher recording density and higher definition.
[0073]
Note that the basic principle disclosed in, for example, U.S. Pat. Nos. 4,723,129 and 4,740,796 is used as a configuration and principle using a means for generating thermal energy as means for ejecting ink. Are preferably performed. This method can be applied to both the so-called on-demand type and continuous type. In particular, in the case of the on-demand type, it is arranged corresponding to the sheet or liquid path holding the liquid (ink). By applying at least one drive signal corresponding to the recorded information and giving a rapid temperature rise exceeding nucleate boiling to the electrothermal transducer, the thermal energy is generated in the electrothermal transducer, and the recording head This is effective because film boiling occurs on the heat acting surface of the liquid, and as a result, bubbles in the liquid (ink) corresponding to the drive signal on a one-to-one basis can be formed. By the growth and contraction of the bubbles, liquid (ink) is ejected through the ejection opening to form at least one droplet. When the drive signal is pulse-shaped, the bubble growth and contraction is performed immediately and appropriately, and thus it is possible to achieve the discharge of liquid (ink) with particularly excellent responsiveness.
[0074]
As this pulse-shaped drive signal, those described in US Pat. Nos. 4,463,359 and 4,345,262 are suitable. Further excellent recording can be performed by employing the conditions described in US Pat. No. 4,313,124 of the invention relating to the temperature rise rate of the heat acting surface.
[0075]
As the configuration of the recording head, in addition to the combination configuration (straight liquid flow path or right-angle liquid flow path) of the discharge port, the liquid path, and the electrothermal transducer as disclosed in each of the above-mentioned specifications, the heat acting surface The configurations using US Pat. No. 4,558,333 and US Pat. No. 4,459,600, which disclose a configuration in which is disposed in a bending region, are also included in the present invention. In addition, for a plurality of electrothermal transducers, Japanese Patent Laid-Open No. 59-123670 which discloses a configuration in which a common slot is used as a discharge portion of an electrothermal transducer, or an aperture for absorbing pressure waves of thermal energy is disclosed. A configuration based on Japanese Patent Application Laid-Open No. 59-138461 disclosing a configuration corresponding to the discharge unit may be adopted.
[0076]
Furthermore, as a full-line type recording head having a length corresponding to the width of the maximum recording medium that can be recorded by the recording apparatus, the length is satisfied by a combination of a plurality of recording heads as disclosed in the above specification. Either a configuration or a configuration as a single recording head formed integrally may be used.
[0077]
In addition, by mounting on the apparatus main body, the ink can be integrated with the replaceable chip type recording head, which can be electrically connected to the apparatus main body and supplied with ink from the apparatus main body, or the recording head itself. A cartridge type recording head provided with a tank may be used.
[0078]
In addition, it is preferable to add a recovery means for the recording head, a preliminary auxiliary means, etc. provided as a configuration of the recording apparatus of the present invention, since the effects of the present invention can be further stabilized. Specifically, capping means, cleaning means, pressurizing or suction means for the recording head, preheating means using a heating element different from this, or a combination thereof, or recording is used. Performing a preliminary discharge mode for performing another discharge is also effective for performing stable recording.
[0079]
In the embodiment of the present invention described above, the ink is described as a liquid. However, an ink that is solidified at room temperature or lower, a softened or liquefied ink at room temperature, or an ink jet may be used. In general, the temperature of the ink itself is adjusted within a range of 30 ° C. or higher and 70 ° C. or lower to control the temperature so that the viscosity of the ink falls within the stable discharge range. Any material may be used if it is liquid.
[0080]
In addition, it is solidified in a stand-by state in order to actively prevent temperature rise by heat energy as energy for changing the state of ink from the solid state to the liquid state, or to prevent ink evaporation. Ink that is liquefied by heating may be used. In any case, by applying heat energy according to the application of thermal energy according to the recording signal, the ink is liquefied and liquid ink is ejected, or when it reaches the recording medium, it already starts to solidify. The present invention can also be applied to the case of using ink having the property of being liquefied for the first time. In the present invention, the most effective one for each of the above-described inks is to execute the above-described film boiling method.
[0081]
Note that the present invention can be applied to a system including a plurality of devices (for example, a host computer, an interface device, a reader, a printer, etc.), or a device (for example, a copier, a facsimile device, etc.) including a single device. You may apply to.
[0082]
Another object of the present invention is to supply a storage medium storing software program codes for implementing the functions of the above-described embodiments to a system or apparatus, and the computer (or CPU or MPU) of the system or apparatus stores the storage medium. Needless to say, this can also be achieved by reading and executing the program code stored in the.
[0083]
In this case, the program code itself read from the storage medium realizes the functions of the above-described embodiments, and the storage medium storing the program code constitutes the present invention.
[0084]
As a storage medium for supplying the program code, for example, a floppy disk, a hard disk, an optical disk, a magneto-optical disk, a CD-ROM, a CD-R, a magnetic tape, a nonvolatile memory card, a ROM, or the like can be used.
[0085]
Further, by executing the program code read by the computer, not only the functions of the above-described embodiments are realized, but also an OS (operating system) operating on the computer based on the instruction of the program code. A case where part or all of the actual processing is performed and the functions of the above-described embodiments are realized by the processing is also included.
[0086]
Further, after the program code read from the storage medium is written into a memory provided in a function expansion board inserted into the computer or a function expansion unit connected to the computer, the function expansion is performed based on the instruction of the program code. This includes a case where the CPU or the like provided in the board or the function expansion unit performs part or all of the actual processing and the functions of the above-described embodiments are realized by the processing.
[0087]
As described above, according to the present embodiment, high-quality recording with excellent gradation can be performed even if the ink density changes.
[0088]
In addition to the variation in the ink density, the density of the recorded portion differs depending on the type of the recording medium, and the density gradation may deteriorate. In this case as well, as described in this embodiment By performing automatic calibration, it is possible to always reproduce and output an image having the optimum density gradation. Further, the optimum distribution table can be selected even if the gradation of reproduced density varies greatly depending on the combination of inks to be overprinted or the combination of ink and recording medium.
[0090]
【The invention's effect】
As described above, according to the present invention, recording is used corresponding to the image density. Combination of multiple types of ink A plurality of types of tables for determining the image are prepared, and an optimum table is selected on the basis of the recording density of the actually recorded test pattern, and processing is performed so as to record an image. Can be recorded.
[0091]
Further, according to the present invention, recording is used corresponding to the image density. Combination of multiple types of ink A plurality of tables storing information for determining the recording density were prepared, and the recording density of the test pattern recorded using each table and the recording density were realized. Multiple types of ink Since the image is recorded using the table with the largest correlation with the density signal level corresponding to the combination of Combination of ink types It is possible to select an image and record an image with good gradation reproducibility.
[Brief description of the drawings]
FIG. 1 is a block diagram illustrating a configuration of an ink jet recording apparatus according to an embodiment of the present invention.
FIG. 2 is a flowchart illustrating an example of image signal processing in an image processing unit of the ink jet recording apparatus according to the present embodiment.
FIG. 3 is a diagram illustrating an example of an ink type distribution table according to the present embodiment.
FIG. 4 is a diagram illustrating a configuration of a main part of a print mechanism of a printer unit of the ink jet recording apparatus according to the present embodiment.
FIG. 5 is a diagram showing an arrangement of ink ejection port arrays of the inkjet head unit in the present embodiment.
FIG. 6 is a diagram illustrating an example of a test pattern print result for automatic calibration in the present embodiment.
FIG. 7 is a flowchart illustrating a flow of automatic calibration processing according to the present embodiment.
FIG. 8 is a diagram illustrating a plurality of ink type distribution tables in the present embodiment.
FIG. 9 is a diagram illustrating a method for evaluating density gradation reproduction characteristics according to the present embodiment.

Claims (6)

An image processing apparatus for recording a pixel have a plurality of kinds of similar color inks having different density with each other,
Storage means for storing a plurality of types of tables that define combinations of a plurality of types of ink used for recording pixels of a plurality of levels of density signal levels;
Recording means for recording a plurality of types of test patterns on the recording medium, each of the plurality of types of density signal levels using each of the plurality of types of tables;
Measuring means for measuring the recording density of each of the test patterns recorded on the recording medium by the recording means;
Based on the recording density measured by the measuring means and the density signal level corresponding to the combination of a plurality of types of inks that realize the recording density, the density gradation reproducibility is the best among the plurality of types of tables. A selection means for selecting a table;
Generation means for generating recording data for recording using the combination of the plurality of types of ink corresponding to the density signal level of each pixel constituting the image data, using the table selected by the selection means; Have
Wherein the plurality of types of tables, the among the plurality of stages of the density signal level, low in density side has set all the same the combination for the same density signal level, more for the same density signal level in the high concentration side, except for the highest concentration the image processing apparatus characterized by defining an of the combination. Said selecting means, according to claim, characterized in that the calculated correlation coefficient between the measured recording density and the density signal level by measuring means, selects the most larger table a correlation based on the correlation coefficient 1 An image processing apparatus according to 1. An image processing method for recording a pixel have a plurality of kinds of ink of different similar colors different concentrations density with each other,
A step of reading out the plurality of types of tables from a storage means storing a plurality of types of tables defining combinations of the plurality of types of ink used for recording pixels of a plurality of levels of density signal levels;
A recording step of recording a test pattern including pixels of the plurality of levels of density signal levels on the plurality of types of recording media using each of the plurality of types of read tables;
A measuring step of measuring a recording density of each of the test patterns recorded on the recording medium in the recording step;
Based on the recording density measured in the measurement step and the density signal level corresponding to the combination of a plurality of types of inks that realize the recording density, the density gradation reproducibility is the best among the plurality of types of tables. A selection process for selecting a table;
Using the table selected in the selection step, a generation step for generating recording data for recording using the combination of the plurality of types of ink corresponding to the density signal level of each pixel constituting the image data; Have
Wherein the plurality of types of tables, the among the plurality of stages of the density signal level, low in density side has set all the same the combination for the same density signal level, more for the same density signal level in the high concentration side, except for the highest concentration an image processing method characterized in that it defines the combination. Wherein the selection step according to claim 3, wherein the measuring the correlation coefficient between the measured recording density and the density signal level in the step, selecting the most larger table a correlation based on the correlation coefficient An image processing method described in 1. A recording apparatus for recording an image on a recording medium have a plurality of kinds of similar color inks having different density with each other,
The image processing apparatus according to claim 1 or 2 ,
Control means for driving the recording means based on the recording data generated by the generating means of the image processing apparatus and controlling to record an image based on the input image data;
A recording apparatus comprising: A recording method for recording an image on a recording medium have a plurality of kinds of similar color inks having different density with each other,
The image processing method according to claim 3 or 4 ,
A control step for controlling to record an image based on the input image data based on the recording data generated in the generation step in the image processing method;
A recording method characterized by comprising:

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